1. Field of the Invention
This invention relates to a tightener to replace idlers on roller chain assemblies.
2. Description of the Related Art
In many applications, roller chain is used to transmit power from a drive sprocket to a driven sprocket. These sprockets each include teeth that mesh with the spaces between rollers on the roller chain.
A chain tightener or idler is usually a part of the system to provide the tension desired in the roller chain. In theory, the idler is adjusted until the roller chain is as taut as desired. Unfortunately, a variety of imperfections result in run-out that causes the chain to whip and lash, increasing wear and noise.
Variance may be found in the chain link itself, in the drive, drive and idler sprockets, any of the three shafts or any of the sprocket teeth. Also, the shaft bearings also contribute to run-out.
Total indicator run (ITR) is the amount of run out from a high to a low point for each component. The individual value can easily be as high as 0.010" (0.025 cm). The composite of all ITR's can be much higher.
Since each component has its own `high` and `low`, it may take many revolutions before all `highs` or all `lows` line up. This variance means that an idler is usually adjusted so the chain is normally slack, and only tight at the highest runout point. Otherwise, the chain would be normally snug, but occasionally too tight when the maximums were reached. This looseness causes more noise, decreases chain life and causes wear on all components.
Whenever chain flexes it wears. Most wear occurs on the slack side of the drive. The tightener of the invention maintains tension holding the chain in a straight line which reduces wear.